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Overview of spin physics results from PHENIX experiment

Overview of spin physics results from PHENIX experiment . The 4th International Workshop of High Energy Physics in the LHC Era Valparaiso, Chile January 4-10, 2012 Kiyoshi Tanida (Seoul National University) for the PHENIX Collaboration.

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Overview of spin physics results from PHENIX experiment

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  1. Overview of spin physics results from PHENIX experiment The 4th International Workshop of High Energy Physics in the LHC Era Valparaiso, Chile January 4-10, 2012 Kiyoshi Tanida (Seoul National University) for the PHENIX Collaboration

  2. Overview of spin physics results from PHENIX experiment The 4th International Workshop of High Energy Physics in the LHC Era Valparaiso, Chile January 4-10, 2012 Kiyoshi Tanida (Seoul National University) for the PHENIX Collaboration

  3. What are we aiming at? • To study proton’s spin structure • The flagship question:“Where the proton spin comes from?” • Proton spin puzzle • Helicity distribution of partons in longitudinally polarized protons, especially gluons • Flavor-decomposed quark helicity distribution using Ws • What’s there in transversely polarized protons? • dq≠Dq • Very hot recently • Needs more than simplecollinear picture to understand

  4. Brahms pp2pp PHENIX STAR The Relativistic Heavy Ion Collider accelerator complex at Brookhaven National Laboratory

  5. RHIC p+p accelerator complex RHIC pC “CNI” polarimeters absolute pH polarimeter BRAHMS & PP2PP PHOBOS RHIC Siberian Snakes PHENIX STAR Siberian Snakes Spin Rotators 5% Snake LINAC BOOSTER AGS pC “CNI” polarimeter Pol. Proton Source AGS Coulomb-Nuclear Interference 200 MeV polarimeter Rf Dipoles 20% Snake

  6. PHENIX Experiment Pioneering High Energy Nuclear Interaction EXperiment

  7. Universidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP05315-970, Brazil Institute of Physics, Academia Sinica, Taipei 11529, Taiwan China Institute of Atomic Energy (CIAE), Beijing, People's Republic of China Peking University, Beijing, People's Republic of China Charles University, Ovocnytrh 5, Praha 1, 116 36, Prague, Czech Republic Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic Helsinki Institute of Physics and University of Jyväskylä, P.O.Box 35, FI-40014 Jyväskylä, Finland Dapnia, CEA Saclay, F-91191, Gif-sur-Yvette, France LaboratoireLeprince-Ringuet, EcolePolytechnique, CNRS-IN2P3, Route de Saclay, F-91128, Palaiseau, France Laboratoire de Physique Corpusculaire (LPC), UniversitéBlaise Pascal, CNRS-IN2P3, Clermont-Fd, 63177 AubiereCedex, France IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, France Debrecen University, H-4010 Debrecen, Egyetemtér 1, Hungary ELTE, EötvösLoránd University, H - 1117 Budapest, Pázmány P. s. 1/A, Hungary KFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (MTA KFKI RMKI), H-1525 Budapest 114, POBox 49, Budapest, Hungary Department of Physics, Banaras Hindu University, Varanasi 221005, India Bhabha Atomic Research Centre, Bombay 400 085, India Weizmann Institute, Rehovot 76100, Israel Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan Kyoto University, Kyoto 606-8502, Japan Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki 851-0193, Japan RIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan Chonbuk National University, Jeonju, Korea EwhaWomans University, Seoul 120-750, Korea Hanyang University, Seoul 133-792, Korea KAERI, Cyclotron Application Laboratory, Seoul, South Korea Korea University, Seoul, 136-701, Korea Myongji University, Yongin, Kyonggido 449-728, Korea Department of Physocs and Astronomy, Seoul National University, Seoul, South Korea Yonsei University, IPAP, Seoul 120-749, Korea IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, Russia INR_RAS, Institute for Nuclear Research of the Russian Academy of Sciences, prospekt 60-letiya Oktyabrya 7a, Moscow 117312, Russia Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia Russian Research Center "Kurchatov Institute", Moscow, Russia PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia Saint Petersburg State Polytechnic University, St. Petersburg, Russia Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Vorob'evy Gory, Moscow 119992, Russia Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden 13 Countries; 70 Institutions Feb 2011 Abilene Christian University, Abilene, TX 79699, U.S. Baruch College, CUNY, New York City, NY 10010-5518, U.S. Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S. Physics Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S. University of California - Riverside, Riverside, CA 92521, U.S. University of Colorado, Boulder, CO 80309, U.S. Columbia University, New York, NY 10027 and Nevis Laboratories, Irvington, NY 10533, U.S. Florida Institute of Technology, Melbourne, FL 32901, U.S. Florida State University, Tallahassee, FL 32306, U.S. Georgia State University, Atlanta, GA 30303, U.S. University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S. Iowa State University, Ames, IA 50011, U.S. Lawrence Livermore National Laboratory, Livermore, CA 94550, U.S. Los Alamos National Laboratory, Los Alamos, NM 87545, U.S. University of Maryland, College Park, MD 20742, U.S. Department of Physics, University of Massachusetts, Amherst, MA 01003-9337, U.S. Morgan State University, Baltimore, MD 21251, U.S. Muhlenberg College, Allentown, PA 18104-5586, U.S. University of New Mexico, Albuquerque, NM 87131, U.S. New Mexico State University, Las Cruces, NM 88003, U.S. Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S. Department of Physics and Astronomy, Ohio University, Athens, OH 45701, U.S. RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S. Chemistry Department, Stony Brook University,SUNY, Stony Brook, NY 11794-3400, U.S. Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, NY 11794, U.S. University of Tennessee, Knoxville, TN 37996, U.S. Vanderbilt University, Nashville, TN 37235, U.S.

  8. The PHENIX Detector • Philosophy • high resolution & high-rate at the cost of acceptance • trigger for rare events • Central Arms • |h| < 0.35, Df ~ p • Momentum, Energy, PID • Muon Arms • 1.2 < |h| < 2.4 • Momentum (MuTr) • Muon piston calorimeter • 3.1 < |h| < 3.9

  9. PART 1: Helicity distributionwith longitudinal polarization

  10. Helicity distribution • Lepton deep inelastic scattering (DIS) experiments • Quasi-elastic scattering of quark and lepton at high energies where perturbation is applicable • Reaction depends on quark spin  spin structure function

  11. Proton spin puzzle • Quark spin carries only 20-30% of the nucleon spin spin puzzle (crisis) • What carries the rest? • Gluon spin? • Orbital angular momentum? 0.2-0.3 Our Main Goal

  12. What we can’t know from DIS • Photon mediated  sensitive to charge2 • u : d : s : g = 4 : 1 : 1 : 0 • Gluon is invisible!(c.f., indirect methods: Q2 evolution, photon-gluon fusion) • Can we see gluons directly? Yes, what we need is a Polarized Proton collider

  13. What we measure? ~ (parton pol.)2× (aLL in parton reaction)

  14. How can we access gluons? • Typical parton level diagrams （LO） • What we actually measure are not partons, but fragmented hadrons • Come from different mix of partons • Parton information （e.g., Bjorken x） is obscured

  15. Some examples • Direct photon: g + q  g + q • No fragmentation • Small contamination (e.g.`qq  gg) • Jet, high-pT hadron production • Mix of all subprocesses • LO  highest statistics  Good measurement with lower luminosity • Heavy quarks (charm, bottom) • gg→`qq is the main process at RHIC • W： sensitive to quark flavors • e.g.,W+ comes from`du

  16. Accumulated data with longitudinal polarization

  17. Results p0 ALL@200 GeV Precision reaches O(10-3), but still consistent with 0 asymmetry Run5 Run6 Run9

  18. PRD76:051106,2007 How to extract Dg(x)? (1) • p0s come from quarks and gluons of various x Deconvolution necessary • Are we sure that we understand contribution of partons? YES! • NLO-pQCD calculationreproduces s well p0@200 GeV, h~0

  19. How to extract Dg(x)? (2) • Practical analysis • Assume functional form: e.g., Dg(x)=Cg(x)xa(1-x)b • Search optimum parameters using data, including DIS. • Ex： GRSV（M. Gluck et al., PRD 63 (2001) 094005.） • Assume DG, other parameters are determined from DIS. • Several versions for various DG（GRSV-std, max, min, ...） • Several other analyses • For the same integral, DG, Dg(x) could be very different • Our measurement mostly constrains DG[0.02,0.3]

  20. G: Global Fit DSSV analysis (Run 9 data not taken into account) Phys. Rev. Lett. 101, 072001(2008) RHIC data • Uncertainty estimation: • 2=1 • 2/2=2% • Node in Dg(x)?

  21. Global Fit including Run9 0 ALL By S.Taneja et al (DIS2011) ala DSSV with slightly different uncertainty evaluation approach DSSV DSSV + PHENIX Run9 0 ALL No node … Uncertainties decreased A node at x~0.1 ?

  22. Extend x-range  different s 0 at ||<0.35: xg distribution vspT bin s=62 GeV 2-2.5 GeV/c 4-5 GeV/c 9-12 GeV/c s=200 GeV  2-2.5 GeV/c 4-5 GeV/c 9-12 GeV/c s=500 GeV

  23.  at s=62 GeV 0: PHENIX, PRD79, 012003 • Very limited data sample (0.04 pb-1, compared 2.5 pb-1 from Run2005 s=200 GeV) • Clear statistical improvement at larger x; extends the range to higher x (0.06<x< 0.4) • Overlap with 200 GeV ALL provides measurements at the same x but different scale (pT or Q2) • s=500 GeV ALLresults will be available soon (from Run2009 with L~10 pb-1 and P~0.4) Charged hadrons

  24. Forward Calorimetry: MPC Muon Piston Calorimeter (3.1 < |h| < 3.9) :lower x10-3 Cluster (p0 dominant) ALL Decay photonπ0Direct photon Fraction of clusters PT

  25.  W measurement Parity Violation Asymmetry Clean flavor separation w/o fragmentation uncertainty

  26. We in mid-rapidity Phys. Rev. Lett. 106, 062001 (2011)

  27. W asymmetry Run 9 data e+ e- Uncertainty is still large More data in 2011 and from now

  28. Resistive Plate Counter (RPC) (Φ segmented) B Forward ーNew Trigger System Trigger events with straight track (e.g. Dstrip <= 1) SG1 Level 1 Trigger Board Trigger RPC FEE MuTRG Data Merge Amp/Discri. Transmit Trigger 5% Optical MuTRG MRG MuTRG ADTX 1.2Gbps Trigger 2 planes RPC / MuTRG data are also recorded on disk. MuTr FEE 95% Interaction Region Rack Room

  29. Trigger efficiency OK: plateau eff. 92% More results ... no time to show them all Run11 data under analysis ーresults coming soon

  30. Part 2:Transverse spin physics

  31. Left xF<0 xF>0 L  R Right Transverse spin physics • Transversitydq: Due to Einstein’s relativity, not the same as Dq • Unexplored leading twist PDF • AN： left-right asymmetry wrt transverse polarization 

  32. Requirements for AN • Helicity flip amplitude & relative phase • In QCD, helicity is conserved if mq=0. AN ~ asmq/pT ~ O(10-3) in naive collinear picture

  33. Reality However, large ANobserved in forward pions. WHY?? We need something more  hot topic

  34. SP SP kT,q p p p p Sq kT,π Possible mechanisms (ex.) (ii) Collins mechanism:Transversity (quark polarization) × jet fragmentation asymmetry (i) Siversmechanism:correlation between proton spin & partonkT Sq Phys Rev D41 (1990) 83; 43 (1991) 261 Nucl Phys B396 (1993) 161 (iii) Twist 3:quark-gluon/gluon-gluon correlation A source for Sivers function Expectation: at large pT, AN ~ 1/pT – not observed so far

  35. Forward -- MPC p0 AN

  36. MPC @ 200 GeV Cluster (p0 dominant) AN Same tendency with other energies and experiments

  37. Forward h AN

  38. Forward h AN same tendency with p0

  39. Comparison with STAR Quite different at high xF Due to slightly different kinematic conditions? Need confirmation/deconfirmation

  40. Midrapidity hadrons AN • AN is zero within 0.1% contrast with forward hadrons

  41. h1 h2 Quark spin _   quark quark h1 h2 Collins fragmentation function h _   quark quark (courtesy A. Bacchetta) h IFF and Collins FF Interference fragmentation function J. Collins, S.Heppelmann, G. Ladinsky, Nuclear Physics B, 420 (1994) 565 J. C. Collins, Nucl. Phys. B396, (1993) 161 FF measurements are ongoing at KEK-BELLE

  42. Asymmetry result • More results ... again, no time to show them all Still need more data...

  43. Part 3:Future measurements

  44. More data! • Goal:> 50 pb-1 @ 200 GeV, > 300 pb-1 @ 500 GeV forward 0 mid rapidity 0 MPC 0 500 GeV 300 pb-1 P=0.55

  45. Wm in forward

  46. More detectors – (F)VTX VTX barrel |h|<1.2 • VTX (from 2011) • FVTX (from 2012) • Study of c & b Gluon polarization via • Larger acceptance Jet tagging • q+g g+jet • Theoretically clean channel • Luminosity hungry FVTX More will be discussed by J. Seele this afternoon

  47. Even further upgrade -- sPHENIX Compact, hermetic, EM + hadroncalorimetry • Forward region is important for • spin physics • AN in forward regions • Dg(x) in small x region Details will be discussed by J. Seele this afternoon

  48. Summary • Gluon polarization • Significant constraints on Dg(x) for 0.02<x<0.3 • Extension toward lower x is important higher energy, forward region • Flavor decomposed quark distribution via W • W e observed in central arm, muon arm follows • Transverse spin physics • Trying to find the mechanism to produce large AN in forward region • Access transversity • More data are still to come

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